1. Field of the Invention
The present invention relates to forming a film on a substrate of an integrated circuit, and more particularly to forming the film on the integrated circuit substrate by atomic layer deposition.
2. Discussion of the Related Art
During fabrication of an integrated circuit (IC), various materials are formed on and removed from the IC at various times. For example, (dry) plasma etching is often used to remove or etch material along fine lines or within vias or contacts patterned on a silicon substrate of the IC. Alternatively, for example, vapor deposition processes are often used to form or deposit a material film along fine lines or within vias or contacts on the silicon substrate. Such vapor deposition processes include chemical vapor deposition (CVD) and plasma enhanced chemical vapor deposition (PECVD).
In PECVD, plasma is used to alter or enhance deposition of the material film. For instance, plasma excitation often results in a reaction forming the material film at a temperature that is significantly lower than a temperature required for producing a similar film by thermally excited CVD. In addition, plasma excitation often activates chemical reactions forming the material film, which are not energetically or kinetically favored in thermal CVD. It is possible to vary both chemical and physical properties of PECVD films over a relatively wide range by adjusting parameters of the PECVD process.
However, as geometries associated with ICs continue to decrease, with via dimensions falling below about 100 nanometers, deposition requirements for the film become increasingly critical. Recently, atomic layer deposition (ALD), which is a form of PECVD/CVD, has been recognized as potentially providing ultra-thin gate film formation in front end-of-line (FEOL) operations, as well as ultra-thin barrier layer and seed layer formation for metallization in back end-of-line (BEOL) operations. During ALD, two or more process gases are introduced alternately and sequentially to form a material film one or more monolayers at a time. However the delivery of each of the process gases should be precisely controlled to form the film.
Further, the size of a feature of the ICs generally decreases at a rate greater than a rate at which a thickness of the film decreases. Thus, an aspect ratio of the feature (i.e., a ratio of a depth to a width of the feature) generally increases as the IC feature size decreases (for example, in the order of 10:1). As the aspect ratio increases, it becomes increasingly important to ensure that components of the film are uniformly deposited within the feature.